Control system for pipe bending apparatus



B. A. HILLS CONTROL SYSTEM FOR PIPE BENDING APPARATUS Filed June 24, 1963 July 5, 1966 n g 3,258,846 Ice A atented July 5, 1966 3,258,946 CONTROL SYSTEM FOR PIPE BENDING APPARATUS Bert A. Hills, Jackson, Mich, assignor to Walker Manufacturing Company, Racine, Wis., a corporation of Delaware Filed June 24, 1963, Ser. No. 289,901 11 Claims. (Cl. 72-20) This invention relates to the art of bending tubes or pipes or the like, and more particularly to tube bending apparatus and methods.

One type of tube bending apparatus with which the present invention is capable of being utilized comprises a reciprocably mounted bending die and associated pressure dies. Tubing to be bent is supported between the bending die and the pressure dies during bending operations. The pressure dies are pivotally mounted for opposite swinging movement as bending pressures are exerted through the bending die. Back pressure is applied to the tubing being bent through the pressure dies and is conventionally applied by fluid cylinders, or the like, suitably connected to the pressure dies. Apparatus as hereinbefore described, is shown in detail in US. Patent No. 2,887,141, issued to B. F. Bower et al. on May 19, 1959, the disclosure of which is hereby incorporated herein by reference.

The primary object of the invention is to provide new and improved means of controlling back pressures during a bending operation.

Another object of the invention is to provide a method of bending tubes wherein back pressures are closely controllable to attain maximum bending results.

The invention principles are hereinafter disclosed in detail by reference to an illustrative embodiment of the invention as shown on the accompanying drawing which is a schematic illustration of a tube bending system incorporating the principles of the invention.

Referring now to the drawing, the bending system is shown to comprise a bending die and a pair of pressure dies 12, 14 which are adapted to cooperatively engage and support a piece of tubing 16, or the like, for a bending operation. The bending die 10 is conventionally reciprocably mounted and actuable by a fluid pressure operable cylinder 18. Pressure dies 12, 14 are rotatably supported on shafts 20, 22 and rotatably driven in opposite directions during downward movement of the pressure die 10 to obtain a wiping action of the pressure dies relative to the tube. Backing pressures are applied to the tubing from the pressure dies 12, 14 by fluid cylinders 24, 26 through connecting rods 28, 30 and fulcrum arms 32, 34.

A fluid control system is associated with the bending mechanism and comprises a reservoir 50 and a pump 52 driven by a motor 54. An outlet passage 55 connects the reservoir to the pump and a passage 56 is provided to convey fluid from the pump to the fluid pressure cylinders 18, 24, 26. A bypass passage 58 having a conventional relief valve 60 is provided to return fluid to the reservoir when predetermined pressures in the system are exceeded. The fluid is alternately delivered from the passage 56 to opposite sides of the cylinder 18 through passages 62, 64 by means of a 4way valve 66. A return passage 68 is provided to convey fluid back to the reservoir 50 and a passage 70 connects the passage 56 to the back pressure cylinders 24, 26 through a control valve 72 and passages 74, 76. In the preferred arrangement, the valve 72 may take the form of any conventional adjustable pressure valve which is suitable for adaptation as hereinafter described. A bypass passage 78 is controlled by a relief valve 80 to return high pressure fluid to the reservoir.

The pressure control valve 72 includes an adjustable restriction or the like (not shown) which controls flow of fluid from inlet line to outlet lines 74, 76. The adjustable restriction is mounted in a casing 81 and is ad justable by control means in the form of a slidably movable, normally outwardly biased, adjusting member 82. Movement of the member 82 in the direction of the arrow 84 is adapted to vary the restriction in the valve and to vary the rate of flow of fluid through the valve from the passage 70. Spring means 85, or the like, may be provided to normally bias the member 82 to the position shown, which may, for example, be a position permitting maximum fluid fiow through the valve to the cylinders 24, 26.

In order to obtain maximum bending results, automatic pressure adjusting means are provided to vary the back pressure exerted through the back pressure dies during the different phases of a particular bending operation. To this end, a sleeve 86 may be threadably mounted on the valve casing 81 in coaxial alignment with the member 82. A pair of brackets 88, 90 are mounted on the sleeve and an actuating rod extension 92 is slidably sup ported in a central bore 93 in the sleeve and protrudes outwardly beyond the end of the sleeve at 94. The inner end of the sleeve may be provided with abutment 95 to receive the end of member 82. A control lever 96 is pivotally mounted at 98 on the bracket and has a pin member 100 threadably mounted thereon for axial adjustment to variably position the end portion 102 which is adapted to engage the end of the extension rod 92 and control the position of member 82. An adjusting screw 106 is provided at the end of the lever 96 and is adapted to provide a stop 108 for engagement with the bracket 88 to limit the initial position of the lever 96. The other end of the lever is pivotally connected to a suitable clevis member 110 at 112. A piston rod 114 is connected at one end 116 to the clevis member and is connected at the other end to a piston mounted in a fluid operable cylinder 118. Spring element 120 is mounted between the clevis 110 and the cylinder 118 to exert a bias on the cylinder and continually bias the piston rod to the outermost position shown. The other end of the cylinder 118 is pivotally connected at 122 to the bracket 90.

The piston in the cylinder 118 is movable therein in the direction of the arrow 124 by means of high pressure fluid delivered through a line 126, a control valve L28, and a line from the outlet side of the control valve 72. The flow control valve 128 may be of any conventional design providing a restricted inlet flow path 132 through the valve to the cylinder 118 and a free flow path 134 through the valve from the cylinder 118. The restriction may be provide by an adjustable movable member 136 which is normally biased outwardly by a spring 138 and is adjustably movable inwardly into restricted position in the flow path 132 by means of an adjusting screw portion 140, or the like.

The strength of spring 120 is greater than the strength of spring 85 in the control valve. In the preferred embodiment the spring 120 is approximately twice as strong as the spring 85. The spring 120 has a strength less than the force exerted by the fluid pressure in the cylinder 118 during all stages of a bending operation. Accordingly, the initiation of flow 0f fluid through the control valve 72 at the start of a bending cycle will, in addition to causing a pressure buildup in the back pressure cylinders 24, 26, create a fluid pressure buildup in the cylinder 118 tending to cause the piston to travel in the direction of the arrow 124 and the control lever 96 to pivot outwardly in the direction of the arrow 142. Movement of the control lever outwardly moves the pin 100 outwardly and permits the control rod 92 to be moved outwardly by the compression spring 85. Outward movement of the control rod increases the restriction in the control valve 72 and simultaneously reduces the pressure flow through the control valve. The rate at which the adjustment in flow through the valve 72 is obtained is controlled by the flow control valve 128. The rate of flow of fluid through the flow control valve 128 is dependent on the setting of the adjusting screw 140. The rate of flow through the flow control valve 128 determines the rate of adjustment of the control valve 72 through the lever 96. Pressure bu ldup in the cylinder 118 is controlled in relation to the time of the bending cycle so that a desired minimum pressure is attained at the completion of the bending cycle. in other words, the pressure buildup in the cylinder 118 is at a maximum at the end of the bending cycle so that minimum back pressures have been attained.

In operation of the system, a fluid such as oil or the like, is drawn from the reservoir 5%) by the pump 52 and delivered under pressure to the 4-way control valve 66 through the line 56. The system may be set up to operate at a predetermined pressure by bleeding fluid through the bypass line 58 at a suitably adjusted position of the pressure relief valve $0. The 4-way valve 66 is of conventional design and is operable to direct fluid to either the upper or lower ends of the bending die cylinder 18 through conduits 62, 64. Downward actuation of the bending die during a bending operation causes pivotal movement of the pressure dies 12, 14 against the back pressure cylinders. The passage means'70 provides a supply of fluid under pressure to the adjustable pressure control valve 128. The amount of fluid passing through the pressure control valve 72 is dependent upon the position of pressure dies 12, 14 since the associated control means continuously adjust the valve 72 in direct response to the amount of pressure in the cylinders 24, 26. During upward movement of the bending die, the high pressure fluid flows to the reservoir through the line '78 and valve 80 from the cylinders 24, 26, the control valve 72, the cylinder 118 and the valve 128. As the fluid is evacuated from the cylinder 118, the spring 114 returns the piston and the piston rod 114 to the outwardly extended position which rotates the control lever 96 and the pin 1% to the starting position of engagement with the control shaft 95. Accordingly, a bending cycle is completed and the apparatus is ready for another bending cycle.

The pressure exerted on the back pressure dies through the control arms 32, 34 and the piston rods 28, 30 is dependent upon the pressure of the fluid delivered to the fluid cylinders 24, 26. The pressure of the fluid delivered to the cylinders 24, 26 .is dependent on the adjusted setting of the member 82 of the control valve 72. In order to provide variable adjustment throughout all portions of rotation of the pressure dies, changes in pressure in the system are directly transmitted into an adjusting movement of the member 82 of the valve. Back pressures may thus be maintained at a constant level or varied as desired during the bending cycle.

Since the subject invention is capable of alternative uses and may take various forms, it is intended that the appended claims be construed to include variations and changes in the illustrative embodiment of the inventive principles except insofar as limited by the prior art.

What is claimed is:

1. A control for tube bending apparatus having bending die means and back pressure means, said back pressure means comprising fluid cylinder means, a fluid system to supply fluid under pressure to said fluid cylinder means, and adjustable valve means to control the supply of fluid under pressure and the back pressure applied by said fluid cylinder, the improvement comprising: adjustment means to variably adjust said valve means between an initial setting at the beginning of a bending cycle producing a maximum pressure in said fluid cylinder means and variable other settings during the bending cycle producing reduced pressures in said fluid cylinder means, and control means operably connected to said adjustment means a d being responsive to the flow of fluid to said cylinder means creating said initial maximum pressure to change the setting of said valve means in a predetermined manner during the bending cycle.

2. The invention as defined in claim 1 and wherein said control means comprises a fluid cylinder, a piston rod operable by said fluid cylinder, connecting means connecting said piston rod to said adjustment means for actuation of said adjustment means during movement of said piston rod, fluid passage means connecting said fluid system to said fluid cylinder downstream of said valve means to deliver fluid under pressure to said fluid cylinder and actuate said piston rod, restriction means in said fluid passage means to control the rate of flow of fluid to said fluid cylinder and to gradually actuate said piston rod and gradually adjust said valve means from the initial setting to the variable other settings so that said fluid cylinder means are initially subjected to a predetermined maximum back pressure corresponding to the initial setting of said valve means and are thereafter subjected to variable back pressures dependent upon the rate of flow of fluid past said restriction to said fluid cylinder.

3. The invention as defined in claim 2 and wherein said restriction means is variably adjustable to vary the rate of flow of fluid from said system to said fluid cylinder and to vary the changes in back pressures obtained during a bending cycle.

4. Apparatus for controlling pressure in a fluid system comprising: adjustable valve means in said system for controlling fluid passages in said system downstream of said valve means, adjustment means to variably adjust said valve means and adjust fluid pressures in said system downstream of said valve means, fluid cylinder means, piston rod means operable by said fluid cylinder means and connected to said adjustment means for actuation of said adjustment means by movement of said piston rod means, passage means connecting said fluid cylinder means to said system downstream of said valve means to receive fluid under pressure in said system for actuation of said piston rod means, and flow control means in said passage means controlling the rate of flow of fluid from said system to said fluid cylinder means so that the pressure in said system downstream of said valve means first reaches a predetermined maximum pressure and thereafter is gradually reduced by adjustment of said valve means in proportion to the rate of flow of fluid from said system to said fluid cylinder means.

5. The apparatus as defined in claim 4 and wherein said flow control means comprises an adjustable restriction, said restriction being adjustable to obtain varying rates of flow of fluid from said system to said fluid cylinder means.

6. Apparatus for controlling pressure in a fluid system comprising: adjustable valve means in said system for controlling fluid passages in said system downstream of said valve means, adjustment means to variably adjust said valve means for varying fluid pressures in said system downstream of said valve means, and opera-ting means connected to said adjustment means for variably positioning said adjustment means, said operating means being operable in response to pressure conditions existing in said system downstream of said valve means.

7. Apparatus for controlling pressure in a flu-id system for a machine during a work cycle comprising: adjustable valve means in said system for establishing a maximum fluid pressure in said system downstream of said valve means at the beginning of a work cycle, adjustment means to establish varying fluid pressures below said maximum fluid pres-sure during the work cycle, and actuating means connected to said adjustment means and operable by fluid pressures in said system downstream of said valve means during the Work cycle.

8. Apparatus for controlling pressure in a fluid system for a machine or the like during a work cycle comprising: adjustable valve means in said system for establishing a maximum fluid pressure in said system downstream of said valve means at the beginning of a work cycle, adjustment means to establish varying fluid pressures below said maximum fluid pressure in said system downstream of said valve means during the Work cycle, fluid cylinder means, actuating means operable by said fluid cylinder means to actuate said adjustment means, passage means connecting said fluid cylinder means to said system downstream of said valve means to deliver fluid under pressure in said system downstream ott said valve means to said fluid cylinder means, and flow control means in said passage means controlling the rate of flow of fluid from said system to said fluid cylinder means to gradually adjust said valve means and change the pressures in said fluid system downstream of said valve means during the 'work cycle.

9. In a tube bending machine control for varying the pressure in backing die cylinders provided by fluid pressure from a central fluid system comprising: fluid passage means for delivering fluid under pressure from the central fluid system to the backing d-ie cylinder-s, control valve means in said fluid passage means for varying the pressure in said backing die cylinders, and pressure actuable adjustment means connected to said fluid passage means and operable by pressure variations therein and operably connected to said control valve means.

10. In a control system for a pipe bending machine comprising: cylinder means for applying back-up pressures to a length of pipe during a bending operation, pump means for supplying fluid under pressure to said cylinder means, fluid delivery means for delivering fluid under pressure to said cylinder means from said pump means, control valve means for controlling the rate of flow of fluid from said pump means to said cylinder means and the pressure applied to the pipe during a bending operation, adjustment means for varying the control setting of said control valve means, fluid operable actuating means for said adjustment means, and control passage means connecting said (fluid operable actuating means to said fluid delivery means to operate said actuating means in accordance With fluid pressure in said cylinder means.

11. The invention as defined in claim 10 and having flow control means in said control passage means to control the rate of flow of fluid to said fluid operable actuating means.

References Cited by the Examiner UNITED STATES PATENTS 2,605,731 8/ 1952- Schulze et a1. 7220 2,709,473 5/1955- Grace et al. 7220 2,989,109 6/1961 Heimberger 72369 3,036,622 5/1962 Hitz 72369 3,147,723 9/ 1964 Williamson 7230 3,209,570 10/1965 Hills 7228 FOREIGN PATENTS 730,286 5/ 1955 Great Britain. 117,013 3/1958 Russia.

CHARLES W. LANHAM, Primary Examiner.

RICHARD J. HERBST, W. H. JUST,

Assistant Examiners. 

6. APPARATUS FOR CONTROLLING PRESSURE IN A FLUID SYSTEM COMPRISING: ADJUSTABLE VALVE MEANS IN SAID SYSTEM FOR CONTROLLING FLUID PASSAGES IN SAID SYSTEM DOWNSTREAM OF SAID VALVE MEANS, ADJUSTMENT MEANS TO VARIABLY ADJUST SAID VALVE MEANS FOR VARYING FLUID PRESSURES IN SAID SYSTEM DOWNSTREAM OF SAID VALVE MEANS, AND OPERATING MEANS CONNECTED TO SAID ADJUSTMENT MEANS FOR VARIABLY POSITIONING SAID ADJUSTMENT MEANS, SAID OPERATING MEANS BEING OPERABLE IN RESPONSE TO PRESSURE CONDITIONS EXISTING IN SAID SYSTEM DOWNSTREAM OF SAID VALVE MEANS. 